Danfoss VLT Active Front End AFE 302, Руководство по эксплуатации

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3 Crane System Design
3.1 Selection of Motor Voltage
The AFE system is designed to regulate a DC voltage of
630x1.08=680 V. 690 V motors are suitable for this system.
When the motors are used in the field weakening region
or with output filters, the motors with less than 650 V are
used.
3.1.1 Selection of AFE & LCL Filter
•
AFE systems are built up based on standard 690
V hardware.
•
Standard AFE hardware runs on 630 V mains
supply and DC-link voltage is 975 V.
3.1.2 Selection of AFE for Different
Applications
•
The frequency converter power size in the flux
application must be one or two sizes higher than
the application needed. Also, the frequency
converter should not be higher than two to
maintain a good resolution on current sensors.
•
The AFE electrical rating should be selected
based on the worst-case total power, including
the overload percentage, rather than a mere sum
of the motor power.
•
Example:
Hoist motors 500 kW @ 650 V - Hoist
drives 800 kW
Travel motors 8x50 kW @ 650 V - Travel
drive 500 kW
Trolley motors 4x55 kW @ 650 V -
Trolley drive 400 kW
AFE/LCL – 1,2 MW continuous, with a
175% overload for a maximum 1 min.
3.1.3 Selection of Output Filter (LC Filter)
•
The output filter is needed because of the long
motor cable configuration.
•
Output filters should be sized based on the
frequency converter's maximum output current.
•
The dU/dt filters can be used up to 100 m to
protect the motor. The sine-wave filters can be
used with any cable length (maximum of 1,000
m).
•
Above 150 m cable length it is recommended to
use a sine-wave filter.
•
The cable length is calculated as the sum of all
parallel cables.
•
Filters must be designed to switching frequency
of the frequency converter. The resonance
frequency, f0, of the filter should be:
10× fout max ≤ f0 ≤
fsw
3
•
The resonant frequency must meet the following
equation, limited by the control frequency, f
con
:
f0< fcon
6
Switching frequency [kHz]
Control frequency 1) [kHz]
1.5 3
2 4
2.5 5
3 6
3.5 7
4 4
5 5
6 6
7 7
Table 3.1 Frequencies
1) The control frequency is an internal hardware frequency.
3.1.4 Selection of Switching Frequency
It is recommended that the switching frequency of AFE
and motor drives shall be equal or an integer multiple of
each other.
3.1.5 Selection of LCL Filter
The AFE system is designed in conjunction with the
recommended Danfoss LCL filters in which the physical
size, power rating and electrical parameters of the filters
are optimized.
If non-Danfoss filters are used, system performance and
stability may be degraded.
3.1.6 Crane Cable Concept
To reduce the high frequency noise on the mains line and
to meet the EMC emission limits, the electromagnetic
coupling should be avoided and the following rules have
to be applied:
Crane System Design Operating Instructions
8 Danfoss A/S © Rev. 05/2014 All rights reserved. MG33X402
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